This study was a prospective, multicenter observational study to describe the surgical outcomes (mortality, post-operative intestinal stricture, intra-abdominal abscess formation, etc.) in ELBW infants with either NEC or IP who underwent initial laparotomy or peritoneal drainage. We also evaluated the ability of surgeons to distinguish NEC and IP pre-operatively and the relevance of this distinction on outcome. Finally, an analysis of the impact of extent of intestinal involvement with NEC on outcome measures is reported.